CreateBloomTextureFragmentShader function
Implementation
ShaderObject CreateBloomTextureFragmentShader(int radius, double sigma) {
String constants = makeGaussianPdfKernelString(radius, sigma);
return ShaderObject("BloomPassF")
..AddVaryingVars([vTexUV])
..AddUniformVars([uDirection, uTexture])
..SetBody([constants, _kernelFragment]);
}